String to Integer

Convert the start of the string s to a whole number, following these rules in order:

1. Skip leading spaces (only the space character).
2. If the next character is + or -, read it as the sign (no sign means positive).
3. Read digits (0 to 9) until the first character that is not a digit or the end of the string. Ignore everything after that.
4. If no digit was read, the result is 0.
5. Clamp the result to the range of a signed 32-bit integer: if it is below -2**31 return -2**31, if above 2**31 - 1 return 2**31 - 1.

Examples

Example 1

Input:

my_atoi('42')

Output:

42

The digits 42.

Example 2

Input:

my_atoi('   -42abc')

Output:

-42

Spaces skipped, sign -, digits 42, then abc ignored.

Example 3

Input:

my_atoi('words 987')

Output:

0

The first character is a letter, so no digit is read: 0.

Constraints

• 0 <= len(s) <= 3 * 10**5
• s contains letters, digits, spaces, + and -.